Fructose and glucose in buckwheat nectar enhance Peristenus spretus (Hymenoptera: Braconidae) survival and parasitism of the mirid Apolygus lucorum

Abstract

Supplementary nutrients such as floral nectar or sugars are important food sources for the fitness and reproduction of parasitic Hymenoptera. Peristenus spretus is the dominant parasitoid of the mirid bug Apolygus lucorum and can exert considerable control of this pest. Previous studies found that the addition of buckwheat (Fagopyrum esculentum) strips in cotton fields improved P. spretus parasitism of A. lucorum nymphs. In this study, we showed that buckwheat flowers prolonged parasitoid lifespan by 1.7- to 3-fold, depending on wasp sex, and increased the daily parasitism rate by 10.3% compared with the control treatment without flowers. Soluble sugars, primarily fructose, glucose, maltose, mannose, raffinose, and sucrose, accounted for 6.3% of nectar weight. Supplementation of the four most common sugars (fructose, glucose, mannose, and sucrose) all had positive effects on P. spretus lifespan and reproduction. Fructose was the most dominant sugar in buckwheat nectar and had the most significant impact on these variables, suggesting it is the most suitable sugar for P. spretus adults. Glucose was the second most abundant sugar in the nectar, and its supplements significantly extended female longevity and the number of progeny produced per female compared to controls. This study identifies the sugars in buckwheat nectar that enhance the survival and parasitic activity of P. spretus, providing insights to potentially enhance biological control of this mirid pest of cotton.